Noun Declinator - Vocabulary levels and better randomization

Hello, today I've added some more improvements to the noun declinator:

Vocabulary levels (A1-C2) - You can narrow down your practice to desired vocabulary levels.

Improved settings UI - When you start the exercise, the current settings are hidden by default so they don't clutter the screen. You can click "show settings" button to show them. In the settings table I've improved how selected cases and words are presented.

Better randomization - The algorithm tries to match an equal number of nouns for each gender and level. For example, if you choose all genders with B1-B2 levels, you get 10 nouns per gender (5 for B1 and 5 for B2).